The present invention relates generally to wall repair compounds which can be sanded to a smooth finish, such as drywall joint compounds, used to repair imperfections in walls or fill joints between adjacent wallboard panels. More particularly, the present invention relates to such a wall repair compound that includes an additive which reduces the quantity of airborne dust generated when the fully dried and hardened compound is sanded, but nevertheless has properties comparable to those of conventional joint compounds.
Interior walls of residential and commercial buildings are often constructed using gypsum wallboard panels, often referred to simply as xe2x80x9cwallboardxe2x80x9d or xe2x80x9cdrywall.xe2x80x9d The wallboard panels are attached to studs using nails or other fasteners, and the joints between adjacent wallboard panels are filled using a specially formulated adhesive composition called joint compound to conceal the joints. The procedure for concealing the joint between adjacent wallboards, and thereby producing a smooth seamless wall surface, typically includes applying soft wet joint compound within the joint or seam formed by the abutting edges of adjacent wallboard panels using a trowel or the like. A fiberglass, cloth, or paper reinforcing tape material is then embedded within the wet joint compound, and the compound is allowed to dry and harden. After the joint compound has hardened, a second layer of joint compound is applied over the joint and tape to completely fill the joint and provide a smooth surface. This layer is also allowed to harden. Upon hardening, the joint compound is sanded smooth to eliminate surface irregularities. Paint or a wall covering, such as wall paper, can then be applied over the joint compound so that the joint and the drywall compound are imperceptible under the paint or wall covering. The same joint compound can also be used to conceal defects caused by the nails or screws used to affix the wallboard panels to the studs, or to repair other imperfections in the wallboard panels, so as to impart a continuously smooth appearance to the wall surface.
Various drywall joint compounds are known for concealing joints between adjacent wallboard panels. Conventional joint compounds typically include a filler material and a binder. Conventional fillers are calcium carbonate and calcium sulfate dihydrate (gypsum), which are used in xe2x80x9cready mixedxe2x80x9d joint compounds, and calcium sulfate hemihydrate (CaSO4-xc2xd H2O; also referred to as plaster of Paris or calcined gypsum), which is used in xe2x80x9csetting typexe2x80x9d joint compounds. Ready mixed joint compounds, which are also referred to as pre-mixed or drying type joint compounds, are pre-mixed with water during manufacturing and require little or no addition of water at the job site. Such joint compounds harden when the water evaporates and the compound dries. Setting type joint compounds, on the other hand, harden upon being mixed with water, thereby causing dihydrate crystals to form and interlock. Setting type joint compounds are therefore typically supplied to the job site in the form of a dry powder to which the user then adds a sufficient amount of water to give the compound a suitable consistency.
In an effort to reduce the dust generation and cleanup problems associated with the sanding of conventional joint compounds, various attempts have been made to develop specialized dustless drywall sanders. The Matechuk U.S. Pat. No. 4,782,632, for example, discloses a drywall sander including a sanding head designed to minimize the release of dust and further discloses attaching a vacuum cleaner to the sanding head to collect the dust. The Krumholz U.S. Pat. No. 4,955,748 discloses a dustless drywall finisher which uses a wet sponge to prevent the formation of airborne dust.
Dust remains a problem, however, when conventional power sanders or hand sanders are used to sand conventional joint compounds. A need therefore exists for a joint compound that can be sanded using conventional sanders without producing a large quantity of fine particles capable of becoming suspended in air but whose properties are nevertheless comparable to those of conventional drywall compounds.
It would therefore be desirable to provide a wall repair compound composition that can be sanded without producing a large quantity of airborne dust. It would be desirable to provide an additive that could be mixed with commercially available joint compounds to inhibit the formation of airborne particles during the sanding procedure without otherwise interfering with the properties of the joint compound. More particularly, it would be desirable to provide a low dust wall repair compound composition including a dust reducing additive that does not bleed into porous materials to which it is applied, and further provide such a wall repair compound that adheres well to a variety of surfaces including conventional wallboard, metal, and plastics such as polyvinyl chloride (PVC).
The present invention provides a wall repair compound, such as a drywall joint compound which, when allowed to fully dry or harden and is then sanded, generates less airborne dust than conventional joint compounds. More specifically, the present invention provides admixing a dust reducing additive to a sandable compound to reduce the quantity of dust generated when the compound is sanded.
The dust reducing additive is typically pre-mixed with the wet joint compound prior to application to the wall surface. Generally, the dust reducing additive reduces the quantity of airborne dust particles having a size of less than or equal to 10 microns to less than 50% of the quantity that would be generated without the additive when the quantity of dust generated is measured using either of the test procedures described below. In certain embodiments, the quantity of airborne dust particles is reduced by at least 75% compared to a mixture without the additive. Most preferably, the level of airborne dust is reduced by more than 90%.
In one embodiment, the average quantity of airborne particles generated by sanding the hardened wall repair compound of the present invention is less than 50 mg/m3 when sanded according to the test procedures described in this specification. In certain other embodiments, the quantity of dust generated is less than about 15 mg/m3, more preferably less than about 10 mg/m3, and most preferably less than about 5 mg/m3.
In one aspect, the present invention provides a sandable wall repair compound composition comprising filler material, binder material, and dust reducing additive means for reducing the quantity of dust generated by the compound when the compound is sanded.
Suitable dust reducing additives include oils, such as mineral oils, vegetable oils and animal oils, surfactants, oleoresinous mixtures, pitch, solvents, paraffins, waxes, including natural and synthetic wax, glycols, and other petroleum derivatives. Other materials which do not fit within the above categories, such as molasses, may also effectively reduce the quantity of dust generated by a wall repair compound.
The wall repair compound formulations include a conventional filler material and a binder material, such as a resin. The wall repair compound may also include a surfactant and a thickening agent. Prior to hardening, the wall repair compound preferably includes a sufficient amount of water to form a mud-like spreadable material which can be applied to the wall surface. The present invention also provides a dust reducing additive which can be admixed with conventional joint compounds to reduce the quantity of dust generated by the conventional compounds during sanding. The dust reducing additive can be used with both drying type (i.e. ready mixed) or setting type joint compounds.
The present invention also provides a joint compound having good tensile strength, sandability, trowelability, plasticity, water retention, cohesiveness, viscosity stability, good hardening properties, good adhesion to metal and PVC, good paint adhesion, resists cracking, has minimal shrinkage, is light weight, low in cost, and has other properties comparable to those offered by conventional joint compounds.
In a specific embodiment of the invention, the dust reducing additive comprises oil. The dust reducing additive may further comprise a mixture of at least two oils, and may further include wax. The mixture of oils may comprise mineral oil and vegetable oil. A preferred mineral oil is Kaydol oil. Suitable vegetable oils include cottonseed oil, linseed oil, coconut oil, olive oil, tung oil, peanut oil, corn oil, and mixtures thereof.
When the dust reducing additive includes oil, the wall repair compound preferably includes a surfactant to help emulsify the oil. The dust reducing additive generally comprises less than about 10% of the wall repair compound total wet weight. Preferably, the dust reducing additive comprises between about 1.0% and about 5% of the wall repair compound by wet weight percent and, most preferably, between about 3% and about 4%. In a specific embodiment of the invention, the dust reducing additive comprises oil and wax, and the ratio of oil to wax in the dust reducing additive is at least about 10:1.
In one embodiment of the invention wherein the dust reducing additive includes wax and oil and the dust reducing additive comprises less than about 0.5% of the compound total wet weight, the dust reducing additive reduces the quantity of dust generated by the compound during sanding at least about 40%. When the quantity of dust reducing additive is increased to about 1.5% of the compound total wet weight, the quantity of dust generated when sanding the compound is reduced at least about 65%. When the quantity of dust reducing additive is increased to about 2.5% of the compound total wet weight, the quantity of dust generated when sanding the compound is reduced at least about 80%. When the quantity of dust reducing additive is increased to about 3.3% of the compound total wet weight, the quantity of dust generated when sanding the compound is reduced at least about 90%. Further reductions in the quantity of dust generated can be achieved by further increasing the quantity of dust reducing additive.
The present invention also provides a sandable low dust drywall joint compound composition comprising filler material, binder material, a dust reducing additive including oil and/or wax, and an effective quantity of a Theological additive to minimize the possibility of the oil from migrating or bleeding into porous substrates to which the joint compound is applied, such as conventional wallboard. The quantity of rheological additive required is the quantity necessary to perform the desired function and depends on the quantity of dust reducing additive present in the formulation. Generally, the quantity of rheological additive is sufficient to eliminate bleeding when the quantity of dust reducing additive is less and 4 wt-% of the wall repair compound total wet weight.
In one embodiment, the rheological additive comprises an organoclay. The rheological additive may comprise bentonite, hectorite, montmorillonite, and mixtures thereof. The joint compound may further include a polar additive. Suitable polar additives include a mixture of methanol and water, propylene carbonate, a mixture of propylene carbonate and water, a mixture of ethanol and water, acetone, g-butyrolactone, or octylphenoxy polyethoxy ethanol. A preferred polar additive is acetone.
The rheological additive generally comprises about 0 to about 1% of the wall repair compound total wet weight, preferably from about 0.05 to about 0.5% and more preferably from about 0.1 to about 0.2%. The Theological additive generally comprises from about 1% to about 10% of the dust reducing additive total wet weight, preferably from about 2% to about 7%, and more preferably from about 3.5% to about 5.5%.
To optimize the effectiveness of the theological additive, a polar additive is also preferably included in the dust reducing additive. The polar additive is generally present in an amount ranging from about 0 to about 0.05% of the wall repair compound total wet weight, preferably from about 0.02 to about 0.04%. The polar additive is generally present in an amount ranging from about 0% to about 4% of the dust reducing additive total wet weight, preferably from about 0.5% to about 2% and more preferably from about 0.6% to about 1%.
The wall repair compound may also include thickeners, wetting agents, preservatives, fungicides and other ingredients found in conventional drywall joint compounds.
In another aspect, the present invention provides a sandable low dust drywall joint compound composition comprising filler material, binder material, and a dust reducing additive comprising a mixture of wax and oil. In a specific aspect of the invention, the dust reducing additive comprises a mixture of wax, oil, a Theological additive, and a polar additive.
The present invention also provides a method of reducing the bleeding of a low dust wall repair compound containing a dust reducing additive with oil by adding a Theological additive to the dust reducing additive. The method may also include adding a polar additive to the dust reducing additive.
These and other features and advantages of the invention will be apparent to those skilled in the art when considered in view of the following detailed description.